Lore

Olenford was a sorcerer revered as the father of sorcery in Melfia, a land rich in the knowledge of sorcery and pyromancy. Despite this, we know that he was in Drangleic because he entered the Undead Crypt and "did away with his humanity".

It is likely that Olenford was a sorcerer from Drangleic who entered the Undead Crypt seeking "knowledge that surpassed mankind's ken" and was successful in some way. He then traveled to Melfia where he established the teaching of sorcery there. A likely outcome as some hold that Melfian sorceries and pyromancies originated in Drangleic in ages past.

Theories

What Olenford discovered in the Undead Crypt.

We do not know what Olenford discovered in the Undead Crypt, but we do know that there were certain spells (Soul Appease, Warmth and Soul Vortex) that are only preserved in the Undead Crypt. These may not be the only spells preserved in the Undead Crypt.

If Olenford is the father of sorcery in Melfia it is likely that the endurance of many basic spells that are taught to us by Carhillion of the Fold and Rosabeth of Melfia, happened because of him.

Olenford's Staff does decent damage with hexes. This may be because Olenford became fascinated with the Dark or perhaps because he left his staff in the Undead Crypt and like Velstadt, it became tainted with the dark. The idea that he "did away with his humanity" seems to indicate that he sought pure sorcery (i.e. the light part of his soul) as opposed to the Dark (as humanity is the Dark Soul's influence in mankind). However, if he was well versed in sorcery then either he was seeking new sorceries as Carhillion of the Fold does, or he was seeking something other than sorcery, like hexes.

Sources

Olenford's Staff
Staff of Olenford the sorcerer. A catalyst for sorceries and hexes. Olenford, revered as the father of sorcery in Melfia, sought knowledge that surpassed mankind's ken, and so ventured into the Undead Crypt, and did away with his humanity. Some hold the theory that Melfian sorceries and pyromancies originated within the boundaries of Drangleic, in ages past.